Pulse flow fuel injection system for turbojet engines



Feb. 24, 1953' AMMANN 2,629,225

PULSE FLOW FUEL INJECTION SYSTEM FOR TURBOJET ENGINES Filed March 8,1948 5 Sheets-Shet 1 24 22 z/ 23' 1'15 1 25 /f 26 30 3/ y IN V EN TOR.

Feb. 24, 1953 R. M. AMMANN 2,629,225

' PULSE FLOW FUEL INJECTION SYSTEM FOR TURBbJET ENGINES Filed March 8,1948 3 Sheets-Sheet 2 x & Q

& I I 5 El Jjj 49 43 z j .56 zV Pal/f1? fflfleff I INVENZJTE R. M.AMMANN Feb. 24, 1953 PULSE FLOW FUEL INJECTION SYSTEM FOR TURBOJETENGINES 3 Sheets-Sheet 5 Filed March 8, 1948 3 99%? Q m 9 W w 1 patentedFeb. 24, 1953 UNITED STATES PATENT OFFICE PULSE FLOW FUEL INJEc'rIoNSYSTEM FOR TURBOJET ENGINES Rolf Ammann, Patterson- Field, OhioAppetite-ion March 's, 1948, Serial No. 13,733.

(Granted under Title 35, U. s. Code (1952);

See. 266') 3 Claims.

The invention described herein may be manufactured and used by or forthe United States Government for governmental purposes without paymentto me of any royalty thereon.

The present invention relates to a fuel injection system or apparatusfor use with jet engines and combustion turbines;

The primary object of the invention is more-- vide a fuel. injectionsystem. of" apparatus for operative association with a turbojet enginewherein the injection apparatus provides means to force the: fuelthrough thS'fllEl feed pipes and injection nozzles and means todistribute the fuel. intermittently to" the" various injection nozzles,and wherein the latter means operates in a predetermined cyclic mannerto effect fuel distribution according to" a definite pattern or plandepending. on the type of engine, number of fuel injection nozzles andpower outputdesired;

A secondary object of the invention is to provide a: fuel injectionsystem for use in atturbojet engine wherein the fuel injection nozzlesare of a type having. a self-cleaning action when actuatedintermittently by fuel flowing: therethrough in surges: or impulses.

A further object of the invention'is to provide a fuel injection systemfor use ina turbojet engine. wherein there is provided a combined fuelpump and fuel distributor havingf drive means which is capable ofsubstantial speed regulation and. wherein the fuel distributor isadapted to supply uniform'quantities of :fuel toa plurality of fuelnozzles in an intermittent and predetermined manner. v

A further object of-the invention is. to provide a. fuel injection.system for asturbojet engine" in which saidsystem includesa'wmultiplicity of intermittently" actuatedfuelinjection nozzles whichare supplied with fuelin a predetermined sequence. and at pressureswhich will ensure proper atomization of the fuel in spite of variae'tions' in the: power settingtof the fuelinject'ion pump-orenginewpowerselector. 7

Another object:- ofu'ther invention is to provide an improved.turbojets. enginesuitable for use on" high speed aircraft andcharacterized by a fuel injection: system which is reliableim operationand which requiresi'aiminimum of maintenanceservice jover. long" periodsOfoperation.

Another object? of the jection systems therefor; l

The above and other objects of the invention will become apparent'uponreading the following detailed description in conjunction with thedrawings; in which:

Fig. 1 is a longitudinal side elevation view partly in cross section; ofturbojet engine provided with afuel injection apparatus embodying theprinciples I of the Dmsentainventien.

Fig.- 2- is a diagrammatic view of the fuel in jection system asusedwith the" engine of Fig. 1.

Fig. 3 is aschematicview partly in cross sec: tion and-showing theprincipal operating components of the present fuel injection and dis-.tribution system.

Fig. 4 is an interior view of the combined pump and distributorcomponent of the fuel injection and distribution system.

Fig. 5 is a longitudinal cross section of a fuel injection nozzleadapted for use in the present fuel injection system;

Fig. 6 is a diagrammatic view of the fuel injection system as appliedto" a turbojet engine. having a single annular combustion chamberprovided with a' plurality ofuniformlyspaced fuel injection nozzles;

Inturbojet engines and combustion turbines there: 15 normally providedone or more combustion chambers. equipped with fuel injection: nozzleswhich are adaptedto atorhize a liquid fueldelivered under pressuretoithe nozzles. The

fuel; is usually kerosene, which requires fairly high pressure for.proper atomization. In 6111-. playing. open nozzles. a high pressureshould: be

maintained onthe fuel at all times, since the invention isto generallyimprove the dependability and operating characteristics of turboj'etengines and fuel in'- the engine is cold when starting. Efiicientperformance of the engine at moderate rates of fuel flow is important,because in cruising at high altitudes the turbojet engine may run forlong periods at moderate power output. Also in gliding from highaltitudes the engine may be at idling speed for some time and ifcombustion is inefficient the combustion chambers may be cooled to suchan extent as to cause cessation of combustion, thus stalling the engine.

Various solutions for the above stated difficulties have been proposed.As an example it has been proposed to use nozzles having two or threefuel openings of different size with means.

to select a fuel opening consistentwith the power setting of the fuelpump. An alternative arrangement is the provision of two or more fuelinjection nozzles in a group with an automatic selector valve to allowoperation of as many nozzles simultaneously as required for the instantpower setting of the fuel pump or fuel throttle valve. Thus it may bepossible to operate each nozzle at an optimum injection-pressure toavoid incomplete atomization of the liquid fuel. It has also been foundthat the open type of injection nozzle is often subject to coking u andthus becomes clogged as thecarbon accumulations build up around the fuelopening. This is especially apt to occur at low rates of flow of thefuel, when there is little chance for the fuel itself to blow the carbonout of the way.

Fuel injection system m use onengine having multiple combustion chambers.plece rotor ZIl-of' duplex design and capable of drawing air fromoutside the' engine according to the 'direction'of the arrows and. thusbuild: ing up air pressure in the annular pressure 2 the nozzles may bedenoted L-2 and Rr-2 for example. The pump and distributor unit 21 isprovided with six fuel outlets A to F which are active one at a time inrotation as indicated by the arrow, to supply fuel to the chambers I toS in clockwise rotation as shown by the arrow. The fuel lines A to Feach connect to groups of three nozzles which are tabulated as follows:

Fuel Line Nozzles A L-l, L-4, L-7 B L-2, L-5, L-S O. L-3, L-6, L-9 'DR-l, 3-4, R-7 E R-2, R-5, R-S F R-S, R-6, R-Q

. if desired, although the speed relation may vary order to open thefuel nozzle.

I tion 7 chamber. 4o

considerably in various engine designs. The spaced fuel injections inthe chambers provide by combustion a continuous series of expansionwaves following so closely on one another as to preclude the possibilityof the spaced injections failing to ignite. At the beginning of eachinjection the fuel pressure builds up rapidly in When the nozzle opensthe fuel is under high pressure and is therefore projected far enough toensure ignition by the previously injected fuel charge as well as byradiation from the heated combus- Of course each chamber is providedwith .a spark igniter for starting the engine, but this feature is notillustrated because it is so well known. By using a plurality of fuelnozzles in each combustion chamber the reliability of the engine isincreased and furthermore chamber 2|. 'Leading from the outer edge ofthe chamber 2| there are a number of combustion chambers 22, each ofwhich encloses a retort or muffle chamber 23 havingi'air inlet andoutlet passages at the opposite ends thereof. At the air inlet end ofthe retort 23 there is provided a pair of fuel injection nozzles,indicated at 24, which dischargeliquid fuel; in the direction ofthe'airflo-w and which are supplied with fuel oil by means of a pair offuel lines 25 and 26. The fuel lines'extend to'a centrally located fueldistributing and pumpingunit forming part of the accessory section I..This unitwill be described in detail below but its function is tosupply fuelto the various fuel. lines in high pres sure surges or pulsesin a-predetermined cyclic manner. One possible arrangement or plan for.the firing cycle is shown in'Fig; .2, where the zles are indicated bythe letters L and R. meaning left and right. Thus the nozzles for cham-.b l y be. e d, L and Rel. for chambe this arrangement permits theseparate nozzles to completely close between fuel injections. By thefiring plan used in the diagram of Fig. 2, each fuel nozzle is operatedonly once while the combustion chambers are going through two completeinjection or firing cycles. Each cycle may be considered a firingsequence beginning with the firing of chamber l and ending with thefiring of chamber 9. Since the rapid action of the fuel distributorprovides an ebb and flow of fuel pressure in the separate fuel lines Ato F, the present system may be aptly termed a pulse flow fuel injectionsystem. The fuel feed lines connecting groups of three nozzles in threespaced combustion chambers and supplyin fuel thereto simultaneously maybe termed common rail fuel distributing conduits.

The combustion waves starting in the chambers .l to 9 proceed toward theoutlet ends of the chambers (see Fig. l), and pass between guide vanes30 of the turbine section IV. These vanes give the hot gases the properdirection so that they may act with greatest effect on the blades 3| ofturbine wheel 3|. The turbine wheel is mounted rigidly on a centralshaft 32 which drives the compressor rotor 20 and also the units of theaccessory section I. The rapid expansion of air and products ofcombustion in the combustion chambers, and also rearwardly thereof, tosome extent, provides a reaction efzfect todriveizthecngine. in adirection opposite seems connected to lever 61 becomes a relativelyfixed point and the lever 61 turnsslightly in response to movement ofthe eccentric 63 by link 69 and bellows HI.

Considering the action of differential 56 more in detail, it will beseen that the power shaft 51 rotates in a clockwise direction thusturning the carrier plate 58 at the same speed and in the samedirection. The planetary gears 59 are of course carried aroundwith theplate 58 and are adapted to rotate on their own pivots by reason oftheir engagement with the ring gear 6|. Now with the ring gear 6!tationary the pinions 59 will be driven in a counterclockwise directionabout their own pivot shafts, looking at the lower side of thedifferential. The pinions 59 will in turn cause the shaft 43. to turnclockwise by their driving engagement with sun gear 60. However lookingat the upper side of the pump and distributor unit, as in Fig. 2, theshaft 43 and rotor 45 will be rotating in a counterclockwise direction;Now if the control motor 65 is turned on and acts through gears 62 and64 to rotate the ring gear 6| in the same direction as the power shaft51 and pump shaft 43, the planetary pinions 59 will be speeded up thusincreasing the rotative speed of gear 60 and shaft 43, As the value ofthe armature resistance 66 is decreased the motor 65 Will go faster andthe pump shaft 43 will also be rotated faster to step up the fuelinjection pressure and the amount of fuel injected in the combustionchambers at each actuation of the fuel nozzles. Expansion of the bellowsby the effect of increased altitude or movement of the manual lever 12to the right will increase the instant value of resistance 66 to reducethe speed of motor 65 and also reduce the speed of the fuel pump. Thespeed control means for the pump and distributor involving adifferential gearing assembly is shown by way of example, it beingunderstood that other types of variable speed transmissions may besubstituted as desired.

Fuelinjection nozzle The various fuel lines A to F terminate in fuelinjection nozzles of the spring-closed type, such as shown in Fig.6.Each fuel injection nozzle 24 is threaded as at 80 to engage similarthreads formed internally of a member 8| which is flanged at 8| toretain the fuel line 82 in connected relation to the nozzle. The hollownozzle is provided with a transverse wall 83 centrally apertured toprovide a valve seat engaged by a ball valve member 84. On the oppositeside of the ball there is a spring retainer 85 having a coil spring 86seated therein. Extending within the spring 86 is a valve stem 81 havinga flange 88 thereon adapted tobe engaged by the upper end of spring 86.Secured within the nozzle is a plug member 89 having a number --of fuelpassages 90 arranged in circular manner about the valve stem 87. Seatedbetweenthe plug member 8t and the flange .88 is a coil spring 9i, whichacts to hold the nozzle closed as will be explained below. As thefuelfl-ows outward under pressure through the fuel passages, it impingeson a series of swirl fins 92 to give the fuel a definite rotary motionbefore it leaves the nozzle and .thus assist in more thoroughatomization of the fuel. The outer end of the hollownozzle is closed byan end closure 93 screw threaded-into secured position as shown. Theclosure 93 is provided with a conical valve seat to. receive the conicalhead portion 94 on the valve stem 81 in closely engag ing relation.

The action of the fuel injection nozzle is fairly obvious but it isnoted that the liquid fuel always fills the interior spaces of thenozzle. When pressure is put on the fuelby the action of the fuel pumpand distributor, the fuel displaces the ball check member 84 and alsoforces the stem 81 outwardly against the compression of coil spring 9!.Thus the valve stem head portion is lifted off its seat and the fuel isforced out in a swirling spray until the fuel pressure again falls tozero by action of the fuel distributor. The exact structure or formationof the valve stem head portion 94 and seat therefor may be variedconsiderably. For instance the parts may have curved mating faces, withthe head portion 94 ap-' proximating a hemisphere. This will prevent thespray of fuel from spreading out too much as it enters the combustionchamber. It is seen also that the nozzle 26 is threaded at 95 to permiteasy securing thereof in the combustion chamber wall.

The self-closing fuel injection nozzle as used in the present inventionis a vital part of the fuel injection system. Even though carbon maycollect on the end portions of the nozzle in the combustion chamber, thevalve seat and comple mental closure therefor are protected from theaction of combustion except when the valve is open. At that time howeverthe outflow of liquid fuel under high pressure effectively prevent anycombustion products from reaching the valve seat or closure 54. Also anycrust or particles around the edges of these parts are blown off by theflowing liquid fuel when the valve opens under fuel pressure. Asexplained previously the spraying or atomizing action of fuel nozzle isalways eflici-ent, because the nozzle does not open until substantialpressure is put on the fuel entering the nozzle. Since the fuel pump andfuel distributor are engine driven the supply of fuel for combus- 7 tionwill always keep pace with engine speed. By providing a variable speedtransmission between the engine and the fuel pump and distributor unit,the fuel quantities delivered to the combustion chambers may be variedsufficiently to provide flexible operation and precise engine control.

The fuel nozzle design as shown and described is only one example of aself-closing fuel injection valve. Other types and constructionsmay besubstituted according to performance requirements. For instance a numberof present day fuel nozzles for diesel engines'would be suitable in manyinstances. One such fuel injection nozzle is shown on page 66 of DieselFuel Injection Systems by Louis R. Ford (1945). Others are shown onpages 119 to 122 of Gemischbildung und Verbrennung im Dieselmotor byAnton Pischinger and Otto Cordier.

Fuel injection system for use on engine having an annular combustionchamber tribution of. liquid fuel to a plurality of springclosed fuelinjection nozzles regardless of the type of combustion chamber. In Fig.6 there is shown in diagrammatic form a possible arrangement of fuelnozzle and fuel distribution plaul for use with a turbojet engine havinga single annular combustion chamber 100 and central' engine shaft- NH;The constructional details of such an engine may be found on page 117 ofGas Turbines and Jet Propulsion for Aircraft 'by G. Geoffrey Smith(fourth edition-4946) For purposes of illustration the engine combustionchamber 100 is provided with evenly-spaced fuel injection nozzles N-l toN-IO all of which discharge into the same combustion'chamber H19 in adirection more or less from the air inlet end to the gas outlet end. Insome "engines of this type there may be twice as 'many nozzles as shownin Fig. 6, since increase in the number of such nozzles gives moreuniform distribution of heat and smoother gas flow to the turbinelocated just behind the combustion chamber. It is understood that thefuel injection nozzles N- to N-| inclusive are of the self-closing typediscussed hereinabove. V

In the fuel distribution plan as shown in Fig. 6 the nozzles arecombined in opposite pairs and supplied by fuel lines G to K The fuellines connect to the fuel pump and distributor unit [2! at the fueloutlets G to'K arranged in circular manner to receive fuel one at atime, in the same way as described with respect to Figs. 2 and 4. Inthis case the fuel distribution is in a clockwise direction as shown bythe arrow on the unit 121. Also the fuel lines are connected so that thefuel nozzles are supplied in this same direction of rotation. The fuellines G to K connect to pairs of nozzles as'tabulated thus:

The firing plan of the combustion process becomes obvious from the tableand from an inspection of Fig. 6. Just as in the first describedembodiment of the invention the fuel pump and distributor unit I21 iscontrolled by a differential mechanism, but is driven by power from theengine main shaft I 0! through a reducing gear.

All the essential details of the fuel injection apparatus are the samein both examples. However with an annular combustion chamber thesequential combustion waves tend to cause a rotative effect on theproducts of combustion as the fuel injections proceed around the chamberin the same direction. This will obviate the necessity of mixing vanesin the chamber and will also result in slightly higher turbine speedsfor the same flow of fuel. While there may be the usual flame anchors ordividing walls between the fuel injection nozzles, these will not extendmore than a few inches rearwardly of the nozzles. As in the constructionof Figs. 1 and 2, the turbine will be so built as to produce rotation ofthe turbine wheel and shaft in the same direction as the sequence ofinjection of fuel and order of firing of the nozzles. This direction isindicated by an arrow between the shaft ml and the annular combustionchamber I00.

The present pulse flow fuel injection system for turbojet enginesprovides a controllable means to meter liquid fuel to a plurality offuel injection nozzles in an orderly and ositive manner. Moreover it isemphasized that the fuel injection nozzles require a positive fuelpressure starting and-idling the engine.

for actuation ana this pressure gua rantee's adequate fuel'injectionpressure capable of atomizing the fuel even at low rates of fuelfiowras' in The self-closing fuel nozzles are also less subject toclogging by carbon-accumulations, as explained above. The invention isnot limited to the use of the specific fuel distribution apparatusshown, but may be practiced with various types of sequentially operatedfuel 'injectorscapable of forcing liquid fuel through the injectionnozzles in a predetermined cyclic manner. The injection pattern toprovide a logical firing sequence may be planned according to theparticular engine and power requirements. The differences in cyclicfiring order in the two illustrated embodiment demonstrate the possiblewide variations in the specific details of the system.

The embodiments of the invention here shown and described are to beregarded as illustrative only and it is to be understood that theinvention is susceptible to variations, modifications and changes withinthe scope of the appended claims.

Icla ini: q

l 1. A fuelinjection system for use in a-turbojet engine having inconsecutive series an air compressor section," a combustion chambersection including a plurality of combustion oham bers circumferentially'arranged aroundthe central aX-is'of'said engine, a turbine section forsupplyingpower through a central shaft to said air compressor section,and an'exhaust section to conduct the exhaust-gases from said turbine tothe atmosphere, said fuel injection system comprising a pair: ofadjacent fuel injection nozzles extending into each combustion chamberat the tip-stream end thereof, each of said nozzles ineluding a tubularbody having an injection aperture at the end of said body within saidchamber and a spring-actuated member in said body to close said aperturewhen the pressure of the fuel 7 within said body is reduced below thecounterpressure exerted by said spring-actuated memher, a fueldistributor having a rotatably mounted member provided with a fueldistributing passage therethrough, mean to continuously connect saidfuel distributing passage to a source of liquid fuel under pressure, arelatively stationary fuel distributing plate contiguous to saidrotatably mounted member and provided with a plurality of fuel passagesequidistant from the center of rotation of said rotatably mounted memberadapted to connect in consecutive order with said fuel distributingpassage, and fuel conduits connecting said fuel passages and saidnozzles to provide for sequential injection of fuel through one nozzleof the combustion chambers proceeding around the engine in one directionbefore sequential injection of fuel through the other nozzle of thecombustion chambers proceeding around the engine in said one direction,the firing sequence in said combustion chambers being so rapid as tomaintain continuous combustion in each chamber whereby there is acontinuing series of expansion waves moving through each chamber towardthe turbine section of said turbojet engine to produce rotation of theturbine and air compressor thereof.

2. A fuel injection system for use in a turbojet engine having inconsecutive series an air compressor section, a combustion chambersection including a plurality of combustion chambers circumferentiallyarranged around the cen- .tral axis of said engine, a turbine sectionfor supplying power through a central shaft to said air compressorsection, and an exhaust section to conduct the exhaust gases from saidturbine to the atmosphere, said fuel injection system comprising a pairof adjacent fuel injection nozzles extending into each combustionchamber at the up-stream end thereof, each of said nozzles including atubular body having an injection aperture at the end of said body withinsaid chamber and a spring actuated member in said body to close saidaperture when the pressure of the fuel within said body is reduced belowthe counter pressure exerted by said spring-actuated member, a fueldistributor having a rotatably mounted member provided with a fueldistributing passage therethrough, means to continuous- 1y connect saidfuel distributing passage to a source of liquid fuel under pressure, arelatively stationary fuel distributing plate contiguous to saidrotatably mounted member and provided with a. plurality of fuel passagesequidistant from the center of rotation of said rotatably mounted memberadapted to connect in consecutive order with said fuel distributingpassage as said member is rotated in one direction about its center ofrotation, a plurality of common rail fuel distributing conduits eachconnected to a separate fuel passage and also connected to a separategroup of single nozzles of at least two spaced combustion chambers, withsaid fuel passages being thus connected in the order of their connectionwith said fuel distributing passage to successive groups of nozzlesproceeding around the engine in one direction, whereby to complete fuelinjection through all nozzles only after two complete injection cycleswherein the first cycle covers injection through one nozzle of eachchamher, and the second cycle covers injection through the other nozzleof each chamber. q, 3. A fuel injection system for use in a turbojetengine having a plurality of combustion chambers therein comprising aplurality of fuel injection nozzles extending into each combustionchamber at the upstream end thereof, each of said nozzleshaving aninjection aperture and a spring biased member normally closing theaperture, a fuel distributor operatively associated with said injectionnozzles and having a rotatably mounted member with a fuel distributingpassage therethrough, means providing a continuous connection betweensaid passage and a source of liquid fuel under pressure, a relativelystationary distributing plate arranged contiguous to said rotatablymounted member and having a plurality of passages therethrough eachadapted to be consecutively aligned with the fuel distributing passage,fuel distributing conduits, each connecting one of said plurality ofpassages and a plurality of single nozzles, each in separate spacedcombustion chambers whereby the respective connected nozzles will besimultaneously and sequentially operated to maintain continuouscombustion.

ROLF M. AMMANN.

REFERENCES CITED The following references are of record in the file ofthis patent:

' UNITED STATES PATENTS Number Name Date 1 1,690,893 Dorner Nov. 6, 19281,854,615 Lasley Apr. 19, 1932 2,157,284 Egersdorfer May 9, 19392,365,636 Hedges Dec. 19, 1944 2,397,357 Kundig Mar. 26, 1946 2,427,845Forsyth Sept. 23, 1947 2,514,513 v Price July 11, 1950 I FOREIGN PATENTSNumber Country Date 251,677 Italy Jan. 26, 1927

